Click on orbiter.log with right mose button than click on properties,when windows open click on change,than select notepad and OK.
After this orbiter log will alway open with notepad...and than you can read it normal.
It's a text file. What you are looking for are any missing meshes. You might see some missing textures but orbiter can live without that - Missing meshes will cause orbiter to crash.
If you are still having problems post the log on here and we can take a look at it.